Background

There was a strong escort, consisting of 36 Escort Group, usually 2 sloops
(Stork and Deptford)
and 7 corvettes
(Convulvulus, Gardenia, Marigold, Penstemon, Rhodedendron, Samphire and Vetch)
under the command of FJ Walker;
this force was augmented by the new escort carrierAudacity, and her 3 escorting destroyers,
Blanckney, Stanley and Exmoor II
plus 5 other warships, the sloops Fowey and Black Swan,
And the corvettes
Carnation and La Malouine:
A total of 17 warships.

Ranged against them was the wolfpackSeeräuber (Sea Robber, or Pirate) of 6 U-boats (U-67, U-107, U-108, U-131, U-434 and U-574), reinforced later by a further 3 boats.

Action

HG 76 sailed from Gibraltar on 15 December 1941, and was reported almost immediately by German agents across the bay in neutral Spain; these were able to report the convoy’s composition, escort strength and departure time.

HG 76 was also sighted later that day by U-74, on route to the Mediterranean, but was lost in poor visibility, while BdU was confused by an agents report that the convoy had returned to port.

The Sea Robbers were arrayed in a patrol line south of Cape St Vincent, but HG 76 was able to pass through he line without detection.

Meanwhile one of the boats, U-127 was detected on a routine ASW sweep by a group of 4 destroyers from Gibraltar; but after a brief but devastating attack U-127 was destroyed, the credit going to the Australian destroyer HMAS Nestor.

On 16 Dec HG 76 was sighted by a Fw 200 Condor patrolling from Bordeaux; from this U-108 gained contact and commenced shadowing whilst the other Sea Robbers closed in.

During the night of the 16th/17th the wolfpack closed in until by morning on the 17th 4 boats were in contact.

However vigorous patrolling by the escorts, and aircraft from Audacity, led to U-131 being detected; she was attacked by Stork, with Penstemon and the 3 destroyers in concert. U-131 was driven to the surface and sunk, though not before shooting down one of the Martlets.

On the night of 17/18th the U-boats attacked again; aggressive counter-measures prevented any hits, while at dawn on the 18th U-434 was sighted by the destroyers; she was attacked
and rammed by Blankney, which was damaged in the process.

During the rest of the day several of the escorts had to leave;
the sloops Black Swan , Fowey, with the corvettes Carnation and La Malouine returned to Gibraltar to re-fuel, while
Blankney departed for repairs, escorted by Exmoor II.

On the night of 18/19 Stanley sighted U-574 astern, shadowing the convoy; she attacked, but was herself torpedoed and sunk.
Stork and Samphire followed up the attack and destroyed U-574, picking up survivors from both.
Also during the night U-108 attacked successfully, torpedoing Ruckinge, which was abandoned, to be sunk later by Samphire.

On the 19th the convoy was attacked by a force of Condors; they caused no damage, but 2 were shot down, and another damaged, by Martlets from Audacity.
Also that day
the Sea Robbers were joined by
3 more boats from Bordeaux,
U-71, U-567 (captained by U-boat ace KL Endrass), and U-751.
Were dispatched to join the sea robbers; they were to arrive on the 21st.
Over the next 3 days
The 3 remaining boats from Seeräuber, U-67, U-107 and U-108 continued to shadow, attacking without result.

On 21st the 3 boats from Bordeaux, and the U-boats again prepared to attack.

Walker attempted to draw off the attack by having Deptford make a demonstration some way off from the convoy;
This was unsuccessful, as some of the merchant ships were confused by the display, and also fired star-shells, revealing their position.
U-567 was able to sink Annavore, while Bigalk, in U-751 sighted Audacity, zig-zagging behind the convoy without her escort. He fired, and Audacity was sunk, hit by 3 torpedoes.
Marigold, Vetch and Samphire counter-attacked, but without result.

Later that night Deptford spotted a U-boat on the surface; she attacked, and dropped depth-charges, with no apparent result; however, post-war analysis revealed that she had sunk U-567.
Following this Deptford collided with Stork, damaging them both.

During 22 Dec U-71 and U-751 remained in contact, to be joined by U-125 (en route to America), while HG 76 was reinforced by the destroyers Vanquisher and Witch.

On 23 Dececember Donitz, shaken by his losses, and the lack of success, called off the attack; U-67, U-107, U-108 and U-751 returned to bases in France.

Conclusion

Despite the loss of Audacity and the 3 other ships, the safe arrival of 30 ships and the destruction of 3 U-boats (U-127 was not included, and U-567 not confirmed until after the war) was judged to be an outstanding victory.
It also confirmed Walker as the Royal Navy’ s foremost expert in anti submarine warfare.

By contrast Adm Donitz and the U-boat Arm was shaken by their losses, particularly Endrass, who was the leading U-boat ace at that time.